image/decoders/EXIF.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef mozilla_image_decoders_EXIF_h
   7 #define mozilla_image_decoders_EXIF_h
   8
   9 #include <stdint.h>
  10 #include "nsDebug.h"
  11
  12 #include "Orientation.h"
  13 #include "mozilla/Maybe.h"
  14 #include "mozilla/image/Resolution.h"
  15 #include "mozilla/gfx/Point.h"
  16
  17 namespace mozilla::image {
  18
  19 enum class ByteOrder : uint8_t { Unknown, LittleEndian, BigEndian };
  20
  21 struct EXIFData {
  22   const Orientation orientation = Orientation();
  23   const Resolution resolution = Resolution();
  24 };
  25
  26 struct ParsedEXIFData;
  27
  28 enum class ResolutionUnit : uint8_t {
  29   Dpi,
  30   Dpcm,
  31 };
  32
  33 class EXIFParser {
  34  public:
  35   static EXIFData Parse(const uint8_t* aData, const uint32_t aLength,
  36                         const gfx::IntSize& aRealImageSize) {
  37     EXIFParser parser;
  38     return parser.ParseEXIF(aData, aLength, aRealImageSize);
  39   }
  40
  41  private:
  42   EXIFParser()
  43       : mStart(nullptr),
  44         mCurrent(nullptr),
  45         mLength(0),
  46         mRemainingLength(0),
  47         mByteOrder(ByteOrder::Unknown) {}
  48
  49   EXIFData ParseEXIF(const uint8_t* aData, const uint32_t aLength,
  50                      const gfx::IntSize& aRealImageSize);
  51   bool ParseEXIFHeader();
  52   bool ParseTIFFHeader(uint32_t& aIFD0OffsetOut);
  53
  54   void ParseIFD(ParsedEXIFData&, uint32_t aDepth = 0);
  55   bool ParseOrientation(uint16_t aType, uint32_t aCount, Orientation&);
  56   bool ParseResolution(uint16_t aType, uint32_t aCount, Maybe<float>&);
  57   bool ParseResolutionUnit(uint16_t aType, uint32_t aCount,
  58                            Maybe<ResolutionUnit>&);
  59   bool ParseDimension(uint16_t aType, uint32_t aCount, Maybe<uint32_t>&);
  60
  61   bool Initialize(const uint8_t* aData, const uint32_t aLength);
  62   void Advance(const uint32_t aDistance);
  63   void JumpTo(const uint32_t aOffset);
  64
  65   uint32_t CurrentOffset() const { return mCurrent - mStart; }
  66
  67   class ScopedJump {
  68     EXIFParser& mParser;
  69     uint32_t mOldOffset;
  70
  71    public:
  72     ScopedJump(EXIFParser& aParser, uint32_t aOffset)
  73         : mParser(aParser), mOldOffset(aParser.CurrentOffset()) {
  74       mParser.JumpTo(aOffset);
  75     }
  76
  77     ~ScopedJump() { mParser.JumpTo(mOldOffset); }
  78   };
  79
  80   bool MatchString(const char* aString, const uint32_t aLength);
  81   bool MatchUInt16(const uint16_t aValue);
  82   bool ReadUInt16(uint16_t& aOut);
  83   bool ReadUInt32(uint32_t& aOut);
  84   bool ReadRational(float& aOut);
  85
  86   const uint8_t* mStart;
  87   const uint8_t* mCurrent;
  88   uint32_t mLength;
  89   uint32_t mRemainingLength;
  90   ByteOrder mByteOrder;
  91 };
  92
  93 }  // namespace mozilla::image
  94
  95 #endif  // mozilla_image_decoders_EXIF_h